Cone press



4 Sheets-Sheet 1 Sept. 7, 1965 H. S. MESSING GONE PRESS Filed May 24, 196s Sept. 7, H 5 M GONE Filed May 24 1965 lll. [I

NNN n@ EsslNG 3,204,551

PRESS 4 Sheets-Sheet 2 MWM HTTOENEY Sept 7, 1965 H. s. MESSING 3,204,551

GONE PRESS Filed May 24, l9 63 4 Sheets-Sheet 5 INVENTOR.

NI r1 I lq HJALMQR .S MESSING l BY H. S. MESSING sept. 1, 1965 GONE PRESS 4 Sheets-Sheet 4 Filed May 24, 1963 INVENTOR. Hmmm? S. MESSING BY ami/JWM HTTOENEV United States Patent O 3,204,551 CONE PRESS Hjalmar S. Messing, New York, N.Y., assignor to The Black Clawson Company, New York, N.Y., a corporation of Ohio Filed May 24, 1963, Ser. No. 282,949 Claims. (Cl. 10U-158) The invention relates to filter presses and, more particularly, to presses of the type using rotary conical disks for extracting Water from paper pulp.

The invention constitutes an improvement over the types of press shown in my U.S. Patent No. 2,793,583, dated May 28, 1957, and in U.S. Patent No. 2,146,158 issued in the name of Charles F. Scherer on February 7, 1939. More particularly, the invention constitutes an improvement over the press disclosed in my application, Ser. No. 44,605, filed July 22, 1960, now U.S. Patent No. 3,105,434, which is hereby made a part hereof by reference.

While certain prior art presses have performed generally satisfactorily, they have certain objections. The rotor disks each comprise a main disk frame which is keyed or bolted to its supporting shaft, a plurality of perforate sector plates fitted and bolted to the frame, and thin screen sheets riveted, screwed or otherwise secured to the -sector plates. The whole assembly of a single rotor comprises hundreds of pieces. The structure is very vulnerable to overloading and to damage by tramp iron, which often accidentally gets into the pulp fed to the press, particularly when the source of the pulp is scrap paper.

In my prior application, the conical disks are journalled in bearing blocks which are supported by parallelogram rock lever assemblies. Each assembly comprises a set of short levers and a set of long levers. The levers are pivoted to the main frame of the press by lower pivots and to the bearing blocks by upper pivots. The long levers are connected at their tops by a tie-rod having a hydraulic jack, which urges the disks together to put squeezing pressure on the pulp fed to the press.

In my prior application, the parallelogram assemblies are shown `as exact mathematical parallelograms, with the axes of the long and short levers parallel, and lines connecting the lower pivots parallel to lines connecting the upper pivots; and with the upper pivots passing through the axes of the rotor shafts. The line of action of the squeezing force exerted by the long rock levers on the bearing blocks is thus removed from the nip or minimum gap of the press where maximum squeezing pressure occurs.

General objects of the present invention are to provide a press having a more rugged rotor and in general to provide a press which is less complicated and less expensive to build and maintain.

According to a preferred form of the present invention, the rotor comprises a fiat disk base made up of a hub and circular liange cast in one piece. The disk base has a series of concentric annular ridges on which is located a single faceplate of heavy gauge stainless steel. The heavy face plate is suitably welded to the disk base.

The annular ridges divide the face plate into annular zones. Each zone of the face plate is provided with a myriad of drain holes. The different zones may be drilled by gang drills having a predetermined pattern so that the ratio of open area to total area is substantially the same in each zone. The squeeze surface of the face plate is provided with annular grooves forming hills and dales, and with radial grooves, to catch and distribute, to the myriad of holes, the water squeezed from the pulp.

3,204,551 Patented Sept. 7, 1965 lCe The disk base has suitable axial drain holes passing therethrough and the annular ridges have suitable radial drain holes passing therethrough, forming a generally hollow structure for receiving expelled water from the face plate and discharging it generally radially. All holes are so arranged as to prevent holding water and pulp which may stagnate and decay.

The squeezing surfaces of the opposed face plates may be so made that the circular hills of one plate are opposite the circular hills of the other plate; or the face plates may be so made that the annular hills on one plate are opposite the annular valleys of the other plate. In either case the pulp matting will form its own line filter. If desired, in cases where the pulp does not mat suiciently, a single, finely perforated, thin screen sheet may be welded to the face plate.

According to a preferred form of the present invention, parallelogram assemblies are used, as in my pending application, but the pivot points are changed so that the parallelogram is not an exact parallelogram in a purely mathematical sense. The upper pivots of the long rock levers of the present invention are placed nearer the bottom of the bearing blocks, and both lower and upper pivots of the short rock levers are raised. The lowering of the upper pivots of the long rock levers places the line of action of the squeezing force exerted by the long rock lever more in line with the nip or minimum gap of the press where maximum squeezing pressure occurs; and the raising of the short lever pivots causes the approaching and separating movements of the bearing block to be more truly axial.

Other objects and features of the invention will be more apparent from the following description when considered with the following drawings, in which:

FIG. l is a side elevation, partly in section, of one type of press having cone disks according to the invention.

FIG. 2 is an enlarged sectional view of the peripheral portions of the cone disks constituting the pressing zone, taken on the line 2 2 of FIG. 3.

FIG. 3 is an enlarged face view of the pressing surface of the cone disks, viewed in the direction of the arrows 3 3 of FIG. 2.

FIG. 4 is a fragmentary end elevation of the cone disk base before assembling the face plate, viewed in the direction of the arrows 4 4 in FIG. 2.

FIG. 5 is a fragmentary view similar to FIG. 2 but showing a modified form of face plate in which the annular hills of one plate are disposed opposite the annular valleys of the other plate.

FIG. 6 is a fragmentary view showing a fine filter screen welded to the face plate.

In the following description and in the claims, various details are identified by specific names, for convenience, but they are intended to be a generic in their application as the art will permit.

Like reference characters denote like parts in the several figures of the drawings.

In the accompanying drawings and description forming part of this specification, certain specific disclosure of the invention is made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

Referring now to the drawings, and more particularly to FIG. l, the press will, first be only generally described, after which it will be described more in detail.

The press comprises essentially a frame 10; and an annular housing made up of a bottom wall 11 and a top wall l2. The walls enclose a pair of perforate conical disks 13 supported by shafts )i4 which are journalled in a bearing blocks 15. A center ring 16 is disposed between the disks 13 forming, with the disks and housing 11, 12, an annular channel or path through which the pulp passes.

The. pulp is fed into the press through an inlet (not shown) in top wall 12 where it enters the annular channel at the point of maximum gap Zd. The pulp is carried by rotation of the disks 13 to the nip or point of minimum gap 21, and thence to the pulp exit (not shown), as will be understood by those skilled in the art.

The shafts 14 are disposed in the same vertical plane and are set on an angle of 7.5 degrees with horizontal. The bearing blocks 15 are suported by rock levers 17, 18, forming a parallelograrn assembly, permitting the disks to have a limited squeezing movement toward and away from each other. A tie-rod 19 connects the parallelogram assemblies. A hydraulic jack 22 is incorporated in the tie-rod 19 to yieldably control the separating and approaching movements of the disks. Pressure is applied to the jack 2.2 by a hydro-pneumatic pressure accumulator Z3.

The rotation of the disks at a speed of, for example, one and one-half revolutions per minute, carries the pulp from the maximum gap to the minimum gap 21; this squeezes the water from the pulp through the perforations in the disks; the water is caught by side Walls Z4 and collects in the bottom of the chamber 25. Water flows out of the machine through exit opening 26 to a suitable point.

The frame 10 may be a single casting or it may be of separate pieces welded together. In each case it may be webbed and ribbed for strength. 1t comprises a main base 27 on which is located the tie member 29 and side plates or guides 28. Side walls 24- rise to a height about even with the axes of shafts 14 and have flared rims 30 to catch water expelled from the upper half of the disks, as explained hereinafter.

Located between the guide frames 28 are the bearing blocks 15 which journal the shafts 14 of the cone disks 13. These bearing blocks 15 are supported by the parallelogram rock lever assemblies. Since these blocks and assemblies are substantially identical, it is only necessary to describe one in detail.

Each rock lever assembly comprises a pair of short levers 17, and a pair of long levers 18. The long levers 13 are fulcrumed to the frame 19 by a pin 33 which passes through both frame guides 28 and both long levers 18. The short levers 17 are similarly fulcrumed by a pivot pin 34 passing through both frame guides 28.

Located between the pairs of levers 17, 18 is bearing block 15. The block 15 is pivoted between short levers 17 by upper pin 35 and between long levers 1S by upper pin 36. Upper pin 35 passes entirely through the bearing block 15 above shaft 14 and through both short levers 17. Upper pin 36 passes entirely through bearing block 15 below shaft 14 and through both long levers 18.

Thus it will be seen that the fulcrums 33, 34 and upper pins 35, 36 connect the frame lil and bearing block 15 in such a way as to permit a swinging movement of the bearing block about the centers of the several pivots which, in turn, permits a limited axial spacing movement of the two cone disks 13. The disks are shown in midposition in FIG. l.

The block 15 comprises a heavy ring 42 supporting radial ball bearing 37 and a heavy ring 43 supporting end thrust roller bearing 38. The rings 42, 43 are connected by sleeve 44 and suitably welded thereto. The shaft 14 is journalled in bearings 37 and 38. The shaft 14 projects through an end wall to support a drive gear 39. A single motor (not shown) drives gear 39. The right hand disk 13 drives the left hand disk 13, through clutch 54 as explained below.

The rotors will now be described. They are generally similar so it is only necessary to describe one. Referring also to FIGS. 3-6, the rotors each comprise in general a cone disk 13 and shaft 14. The disk 13 comprises a F 4 base 50 and a face plate 51 welded to the base. The base has a hub 52 set on shaft 14. The base and shaft are shown as separate pieces welded together, but these parts may be made up as a one piece casting.

The disk base 5i) comprises a hub 52 and a circular flange 53. Projecting from the hub and welded thereto is a segmental prong clutch 54. Surrounding the hub 52 adjacent the shaft is an annular trough 55. Surrounding the hub on the other side are a series of annular ridges 56 separated by annular grooves 57. The annular ridges 56 are separately denoted by I, II, lll and lV and divide the face plate into three annular zones A, B, and C. Surrounding clutch 54 is annular groove 6i).

The ridges 56 have a series of radial drain holes 58 and the disk flange 53 has a series of axial drain holes 59. In discussing the various drain holes, grooves and channels, reference will be made to axial to dene those conduits extending generally parallel to the axis ,of the shaft and to radial to define those conduits extending generally perpendicular to the shaft. These conduits are not exactly axial, or radial, because the squeezing surface of the disk is conical. However, the cone departs from a ilat plane by such a small angle that these terms are usefully descriptive.

The face plate -51 is connected to the disk llange 53 in the following manner. The inner and outer margins of face plate 51 have annular seats 8S, 39 to receive the inner and outer annular ridges I and IV for the purpose of centering the plate `51 on the iiange 53. The face p-late 51 has intenmediate annular seats 90 to receive intermediate annular ridges II and lll. The seats 9i) may be slightly wider than the intermediate ridges Il and Ill. to eliminate need for a close machine lit. The purpose of all four annular ridges 56 is to support the face plate S1 uniformly along the lengths of the ridges against the tremendous squeezing pressure applied to the pulp passing through the machine. Welding 72 lat the inner and outer margins of the face plate -51 connect plate 51 and flange 53 to form a unit-ary structure.

The outer and inner rims of the face plate 51 have sealing relation, respectively, with the upper and lower cylindrical 'walls 11,112 on the outside, and wit-h the center ri-ng 16 of the housing on the inside. Contacting surfaces are hardened to reduce wear. These surfaces maintain seals 75, 76 (iFlG. l) while permitting the axial squeezing movement 'of the disks 13 relative to the stationary wall 11, 12 and to r-ingr16.

The face plate 51 is preferably made from a flat heavy stainless steel plate. The central circular opening 63 and the outer lcircular edge 64 may be cut by a blow torch. VThe myriad of holes 65 are drilled in the plate while in flat form, after which the plate is dished to conical form, yand then fitted and welded to the cone base. The .assembly may then be annealed and machine finished. The axes of the hol-es 65 are thus perpendicular to the conical face of the plate 51.

Each drain hole 65 comprises a smaller diameter orifice `portion 66 and a larger diameter relief portion 67. To obtain high discharge coefficient of water, the length of the orifice portion 66 should not be longer than its diameter. These holes are drilled from the back side of the face plate (remote from the squeeze sur-face). The larger relief holes 67 are drilled first and then the smaller orilice holes 66.

The squeeze surface of the `face plate 51 has a series of circular and radial grooves. The drain holes 65 are laid out in circular rows `which intersect the bottoms of the circular grooves 68. The circular grooves 68 (and circular rows ocf holes 65) are equally spaced. The circular grooves 68 form circular hills between the grooves, providing a wavy hill-and-dale effect. The supporting annular ridges 56 are sufficiently narrow to engage the face plate 51 along circular lines between the rows of circular holes (see especially ridges II and Ill in FIG. 2). Hence, there are no dead spots to block flow of Water through the holes.

The spacing of the holes may be uniform in any particular row. The holes in each zone A, B or C may be laid out on radii of the disk so that the spacing of the holes circumferentially is progressively greater with increase in distance from the shaft 14 in the particular zone. The spacing of the holes in the row of least diameter in zone A will therefore be equal to the spacing between holes in the row of minimum diameter in zones B and C. The holes in each row of a particular zone are staggered with respect to the holes in adjoining rows,

It will be understood that, although three zones and a particular hole pattern are disclosed for purposes of illustration, any number of zones may be used, and the hole pattern may be varied.

The myriad holes 65 in each zone A, B, C may be drilled by a gang drill. The several drills making up the gang have a predetermined pattern, subject to slight adjustment of the distance between individual drills.

With such an arrangement the same pattern spacing of drain holes 65 as above described, ma-y be used in each zone, even though the zones vary in Iwidth (radially) and in length (circumferentially). This provides a hole pattern having the same ratio of open area to total area in each zone.

As shown in FIG. 3, the squeeze surface of the face plate 51 is also provided with a series of radial grooves. These grooves may extend from the inner to the outer edge of the face plate als at 69, or they may extend across a single zone, or two zones only as at 70j. In the latter Acase the radial grooves of the several zo-nes may -be staggered. In any event, the radial grooves help distribute water across the face plate and help provide more uni- 'form drainage. They also help to grip the mat of puhp as the rotating disks move the pulp from entrance to exit.

As shown in FIG. 2, the circular grooves 68 of one disk may be in register with the circular grooves 68 of the other disk, this places the opposed circular hills in register and provides more squeezing pressure. The radial grooves of one disk may be in register with the radial grooves of the other disk. This arrangement makes possible the manufacture of identical rotors, and is especially adapted yfor heavy duty machines requiring greater squeezing pressure.

Referring now to FIG. 5, if desired, the circular hills 73 of one r-otor may be placed in register with the circular grooves 74 of the other rotor. In this case the rnyriad holes 65 may pass through the circular hills 7-3 of one rotor. The staggered disposition of circular hills and dales on the ltwo opposed face plates 51 is Ipreferable ifor smaller machines generating less pressure.

Referring now to FIG. 6, in some cases the face plate 51 may be covered with a screen 77, particularly in cases where the pulp is not suiciently fibrous to resist passing through the relatively large holes 65 in the face plate. The screen 77 may be used with either the form having the hill-to-hill confrontation shown in FIG. 2 or the hill-to-valley confrontation shown in FIG. 5. In either case the screen 77 is a single disk of substantially the same area as the face plate 51.

The screen 77 is welded to the face plate 51 at the outer rim as at 78 and at the inner rim as at S2. The screen is also welded as at 79 at intervals to the tops of the hills through holes in the screen.

It will be noted that the axes of the shafts 14 intersect at center 85 (FIG. l) in a vertical transverse plane 86 perpendicular to the vertical longitudinal plane in which the said axes lie. These axes are disposed at an equal angle, for example, 7.5 with a horizontal plane.

The conical squeezing faces of the disks are disposed at the same angle 7.5 with respect to planes perpendicular to the shaft axes, as the shaft axes make with horizontal. The conical elements of the squeezing surfaces of the face plates 51 are thus parallel to each other at their lowermost position at the minimum gap 21, and at an angle of 15 with each other at their uppermost position at the maximum gap 20.

The center of gravity of the pulp space is located outward of the half-way point between center ring 16 and the outer cylindrical walls 11, 12. The points 20 and 21, indicating maximum and minimum gaps, also indicate the center of gravity of the pulp space.

A single drive motor (not shown) of the order of 30 H.P. may drive the disks at a speed of 1 to 2 r.p.m. This applies tremendous torque to the bearing blocks 15 and to the rock levers 17, 18. This torque is effectively resisted by the pedestal guides 23. The rock levers 17, 18 slidably engage both guides 28 and bearing block 15.

The clutch segments 54 of the two disks interengage to enable the single motor driving gear 39 to drive both disks.

The teachings of the invention may be applied to machines of various diameters, squeezing pressures and capacity. Certain sizes and dimensions are given for a typical machine for the purpose of assisting in understanding the invention and not in any limiting sense.

A typical machine may be used for squeezing water from kraft pulp having an in-feed density of from 8% to 15%; that is to say, 100 lbs. of wet pulp contain 8 to l5 lbs. of pulp on a bone dry basis and 85 to 92 lbs. of water. The density of the discharged pulp may be 45% t0 50% on a bone dry basis. It requires tremendous pressure to de-water this pulp between these density ranges. Such pressure may run from 2000 to 4000 p.s.i. at the nip.21.

Such a press may have a capacity of tons per 24 hours of kraft wood pulp on a bone dry basis and the pressure applied by the rotors to the shaft and bearings may be about 150,000 lbs. The bearings and parallelogram arrangement will take the whole brunt of this force, the main frame taking about 120,000 lbs. and the tie rod and hydraulic jack taking about 30,000 lbs. in the form shown.

A typical machine may have the load spread over a 60 sector, that is, 30 on either side of the nip 21. The load distribution applied by the face plate 51 to the rotor base 50 may be somewhat as follows: ridge I, 28,500 lbs.; ridge II, 33,500 lbs.; ridge IH, 40,500 lbs.; ridge 1V, 47,500 lbs.

The screen 77 may be a perforated metal plate of, for example, /l thick having holes of, for example, %2" in diameter and an open area of about 30% of the total area. The screen should be sufficiently strong, and the annular hills of the face plate 51 sutiiciently close, that the scren will not bend into the valleys under the tremendous pressures generated at the nip of the press.

The overall diameter of the cone disks 13 may be about 48". The inside diameter of the face plate 51 may be about 24". The drill pattern may provide from 2500 to 3000 drain holes 65 in each face plate. The ratio of open area to total face plate area may be 9% to 15% depending upon the number and diameter of holes. The orifice portion 66 of the holes may vary from Ms to 5/16" in diameter and the relief portions 67 may have 3%" diameters in each case. The face plates 51 may be 1" thick.

The absolute size of the myriad drain holes must be related to the type of material being treated. For paper pulp the libres form their own mat which will act as a screen, so that larger holes can be used for paper pulp than when treating other materials such as slaughter house offal. When treating some materials forming pulp of a very ne texture, the additional screen 77 shown in FIG. 6 is desirable.

The invention has numerous advantages. The heavy stainless steel face plate is not vulnerable to overloading nor to foreign material such as tramp iron. The face plate, welded to well tted circular ridges, forms a boltless structure which can be dimensioned to well resist the high unbalanced pressures applied to the disks. The back side of the disk is well drained, offering negligible resistance to discharge of the large volume of water from the squeeze faces to the ltrate space.

The pulp mat, when suiciently squeezed, will form its own ine filter for passage of water toward the drain holes in the face plates. The equal spacing of openings covering the entire disk face area provides uniform dewatering of the pulp or other material treated. There are no unused squeeze areas. No sector division space is lost. There are no bolt heads.

The inexact parallelogram arrangement places the line of squeezing pressure exerted by the upper pivots 36 of the long rock levers 18 close to the maximum pressure area at the nip 21 and provides a close approximation of axial movement of the blocks 15. The clearing of shaft 14 by both upper pins 3S, 36 permits use of a single pin for each pivot, passing through the block and the branch lever on either side.

Suitable safety devices may be used to help protect the machine against damage. Damage may be caused by excessive pulp feed rate, or by accidental inclusion in the pulp feed of foreign objects, such as tramp iron, or by both. These atfect the machine either by spreading the cone disks apart to cause overspacing at the nip (point of minimum spacing in the annular pulp zone) or by overloading the drive motor.

It is therefore important to stop the machine before damage results. Safety devices may take the form of limiting switches for stopping the pulp feed, or for stopping the electric drive motor, when a certain predetermined safe spacing at the nip 21 is exceeded, or by using the normal overload switch of the drive motor to stop the machine when a predetermined load is exceeded.

The press has uses in addition to squeezing water from Wood pulp. It may be used for extracting other liquids from other materials that are amenable to operation of this press, as for example, food stuffs, sugar cane, slaughter house otfal etc.

It will be noted that the entire rotor assembly, shaft 14, disk base S0, clutch 54, face plate 51, and, when used, screen plate 77, comprises a single integral structure, providing a unitary rotary construction. Shaft, base and clutch may be cast in one piece, or these parts may be constructed in several pieces and suitably welded together in the manner shown.

The several holes in the rotor, that is to say the holes 59 in cone base 50, holes 58 in ridges 56 and the myriad holes 65 in the face plate facilitate cleaning the machine of pulp or other filter cake, thereby preventing these materials from lodging in the machine. In fact, a steam or water hose may be inserted in the axial drain holes 59 in the cone base 50 at the top of the machine, as the rotor slowly turns, to flush out the machine.

While certain novel features of the invention have been disclosed herein, and are pointed out in the annexed claims, it will be understood that various omissions substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

I claim:

1. In a press, a frame, a pair of disks having confronting faces arranged at an angle to each other and defining a pressing zone, each disk having a central shaft remote from said pressing zone, bearing journaling said shafts, at least one bearing comprising a movable block, a rock lever assembly supporting said bearing block; said rock lever assembly comprising a rst lever device, lower pivot means connecting said lirst lever device to said frame, upper pivot means connecting said first lever device to said bearing block at a point offset from its shaft, a second lever device, lower pivot means connecting said second lever device t-o said frame, upper pivot means connecting said second lever device to said bearing block at a point offset from its shaft, a pressure device urging said disks together, whereby pressure generated by the material squeezed by said disks is resisted by said pressure device.

2. In the press of claim 1, each said lever device comprising branch levers on either side of the bearing block, each said upper pivot means comprising a pin passing through the bearing block and through its respective branch levers.

3. In the press of claim 1, said first lever device being remote from said pressing zone, said second lever device being adjacent said pressing zone, the upper pivot means of said rst pivot device being located under said shaft, the upper pivot means of said second lever device being located above said shaft.

4. In a rotor for a lter press, a frame comprising a plate-like base and a hub portion, said base having a series of supporting portions projecting axially from said base, said supporting portions being spaced to provide drainage passages therebetween, a heavy one-piece face plate having an outer edge and a central opening providing an inner edge, said face plate having an annular squeeze surface describing a complete circle, said squeeze surface having a myriad of drain holes passing therethrough, means securing said face plate to said supporting portions at its inner and outer edges, the suppporting portions under said squeeze surface engaging said face plate only at limited areas to minimize obstruction to said drain holes, the spacing of drain holes at said limited areas being no greater than the spacing of holes at places between said supporting portions.

5. In the rotor of claim 4, said supporting portions comprising annular ridges, said annular ridges dividing said squeeze area into annular zones, the ratio of open area provided by the drain holes to total area being substantially the same in the several zones.

References Cited by the Examiner UNITED STATES PATENTS 271,161 1/83 Treber 100-158 1,040,842 10/12 Anderson 1GO-158 1,826,729 10/31 Carver 100-116 2,146,158 2/39 Scherer 100-158 2,793,583 5/57 Messing 100-158 X FOREIGN PATENTS 109,114 8/75 France.

65,492 4/50 Netherlands.

WALTER A. SCI-IEEL, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,204,551 September 7, 1965 Hjalmar S. Messing It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 51, for "Soren" read screen column 8, line 2, for "bearing" read bear'lngs Signed and sealed this 27th day of September 1966.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

4. IN A ROTOR FOR A FILTER PRESS, A FRAME COMPRISING A PLATE-LIKE BASE AND A HUB PORTION, SAID BASE HAVING A SERIES OF SUPPORTING PORTIONS PROJECTING AXIALLY FROM SAID BASE, SAID SUPPORTING PORTIONS BEING SPACED TO PROVIDE DRAINAGE PASSAGES THEREBETWEEN, A HEAVY ONE-PIECE FACE PLATE HAVING AN OUTER EDGE AND A CENTRAL OPENING PROVIDING AN INNER EDGE, SAID FACE PLATE HAVING AN ANNULAR SQUEEZE SURFACE DESCRIBING A COMPLETE CIRCLE, SAID SQUEEZE SURFACE HAVING A MYRIAD OF DRAIN HOLES PASSING THERETHROUGH, MEANS SECURING SAID FACE PLATE TO SAID SUPPORTING PORTIONS AT ITS INNER AND OUTER EDGES, THE SUPPORTING PORTIONS UNDER SAID SQUEEZE SURFACE ENGAGING SAID FACE PLATE ONLY AT LIMITED AREAS TO MINIMIZE OBSTRUCTION TO SAID DRAIN HOLES, THE SPACING OF DRAIN HOLES AT SAID LIMITED AREAS BEING NO GREATER THAN THE SPACING OF HOLES AT PLACES BETWEEN SAID SUPPORTING PORTIONS. 